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Geological Audit Services, Inc. <br /> �.� g <br /> 1803 W March Lane, Suite A•Stockton, CA 95207• (209)956-0264• FAX (209)956-0700 <br /> �iv <br /> PROPOSED MITIGATION OF HYDROCARBON CONTAMINATION <br /> PACIFIC GAS <br /> 2088 Mariposa Road <br /> Stockton, California <br /> EXECUTIVE SUMMARY <br /> In May of 1990, five underground storage tanks (UST' s) and <br /> their appurtenant piping were removed from the site. Soil samples <br /> collected from beneath the tanks and piping indicated that an <br /> unauthorized release of hydrocarbons had occurred. Total petroleum <br /> hydrocarbons (TPH) and volatile aromatics (BTE&X) were detected in <br /> the soil samples at levels as high as 6, 200 parts per million <br /> (Ppm) . <br /> In March of 1993 , GEOLOGICAL AUDIT SERVICES, INC. (GeoAudit) <br /> performed a soil boring site assessment of the property. A total of <br /> nine borings were drilled around the tank excavation(s) and piping <br /> areas. No significant contamination was encountered during the site <br /> assessment. However, hydrocarbon contamination may still be present <br /> beneath the floor of the excavation. <br /> • GEOAUDIT proposes to excavate any remaining contaminated soil <br /> from the floor of the tank excavation. We anticipate removing 500 <br /> cubic yards of soil from the excavation. Contaminated soil will be <br /> placed on plastic and stockpiled on the property. When the <br /> excavation is completed, the stockpiled soil will be covered with <br /> plastic sheeting. Excavated soil will be monitored during removal <br /> using a photo-ionization detector (PID) . <br /> The excavated soil will be sampled and analyzed by a state- <br /> certified laboratory for the presence of petroleum hydrocarbons. <br /> The soil will then be transported to an appropriate landfall <br /> facility or treated on-site (depending upon the analytical <br /> results) . <br /> • <br /> Environmental Services . Hydrogeology•Geotechnical Services <br />